LUNAR TIDAL EFFECTS ON ZONAL AND MERIDIONAL EQUATORIAL ELECTROJET CURRENTS

Significant lunar tidal oscillations have been shown to be present in all the three H, D(= Y) and Z components of the geomagnetic field at t he equatorial station Kodaikanal. The variations in H and Y fields are shown to be nearly opposite in phase to each other even on the indivi dual lunar age group days. The variations are significant only during the solar daytime hours. Seasonally, the largest amplitude of lunar ti des in H as well as in Y field is seen in winter than in summer months even though the solar daily variation in Y is greatly reduced during winter as compared to that in summer months. These tidal variations ca use significant changes in the direction as well as in the magnitude o f equatorial electrojet current. It is suggested that the meridional c urrent is an integral part of the electrojet current. An increase of e astward electrojet current is associated with an increase of poleward current at equatorial north latitudes in India.